Nina Raine's debut as a playwright was a low-key affair. After spending three years unsuccessfully touting her play Rabbit around London's key theatres, she finally directed it herself in 2006, in a room above a pub little bigger than a hutch. But the smallness of the space emphasised the excoriating quality of Raine's dialogue, as her ferociously opinionated characters argued about sex, envy and the torment of ageing. It won Raine two prestigious playwriting awards, transferred to London's West End, and later travelled to New York and Australia. With her second play, Tiger Country, finished before Rabbit reached the stage, Raine was all set to become one of British theatre's most prominent new writers. Instead, she disappeared.

Well, not completely. She spent the next four years writing pilots for TV and building up her profile as a director, notably of Alia Bano's Shades at London's Royal Court last year. But now Raine the playwright is returning to the stage. Tiger Country will get its premiere at London's Hampstead theatre in January. Before that comes another new play, Tribes, which opens at the Royal Court this month. As in Rabbit, the characters are scathing and anta-gonistic – although here, arguing is seen as proof of love. The irony is that Raine hates conflict. "I'm quite a coward: I'll do anything to avoid an argument."

Tribes revolves around a deaf character, Billy, who struggles to make his feelings known in a family too busy shouting to pay him proper attention. Its most compelling character, however, is the family's overweening patriarch, Christopher. A foul-mouthed, bull-headed academic, he vilifies everything from pear juice to his son's girlfriend, but takes special pleasure in denigrating northerners, deaf people and other writers, particularly those who succumb to cliche.

Could this possibly be a portrait of Raine's father, the famously caustic critic and poet Craig Raine? Not a bit, says Nina. "My godfather [who happens to be novelist Julian Barnes] said, 'Oh God, it's so not Craig.' Christopher is more pompous. He's written books on words. My dad wouldn't dream of writing a book about fucking words." Still, when Nina told her father that most people who have encountered the play so far find Christopher monstrous, he replied: "No, he's not, he talks a lot of sense."

Raine's own writing career started young: "When I was five, I wrote amazing stories about pirates. But then you get a bit self-conscious and lose a sense of your own voice." She tried writing short stories again after university, supporting herself by working as a waitress at the River Cafe, but made little progress. It was her parents who were obliquely responsible for her change in direction. While travelling during her year out, Nina reported conversations she heard on train journeys to her mother, a retired Oxford tutor, who praised her ear for dialogue. And in 1996, her father's adaptation of Racine's Andromaque appeared at London's Almeida, directed by Patrick Marber. "It was so exciting, and I suppose that put the idea in my head."

She learned a lot about playwriting by working as an assistant director, to the likes of Nicholas Hytner, Stephen Daldry and Katie Mitchell. Now 34, she hasn't assisted for five years, and misses it a little: "It's great for a writer, because you have lots of slightly dreamy brain time, yet there's constantly something interesting happening." She's been relishing the chance to see into director Roger Michell's "bag of tricks" as he prepares Tribes for the stage. Plus, it's a lot less stressful than directing the play herself: "That's like going from one end of London to the other on public transport – when Roger directs for you, it's like being driven in a limo."

Not that she's had much experience of limos: her life has not been a pecunious one. "My family were really hard up, but it didn't ever seem to be a worry," she says. "So I don't worry about money at all – I worry about time." It frustrates her that the bulk of the last six years were spent looking for homes for Rabbit and then Tiger Country. Yet she would never give up writing to become a full-time director: "You don't have enough control. Directing is mainly about offering people jobs and them turning them down. At least with writing you have the control of what you put down on the page."

And at least writing brought her a windfall: the £30,000 Evening Standard award for most promising playwright. Raine ploughed the money into a deposit on a flat in south London, which she shares with one of her three younger brothers, 26-year-old Moses. He is also a playwright, and the siblings help each other with their work. "Today is a perfect example: I woke up and Moses was already writing, I said 'hi' and he said, 'At what point should I put an interval?'" In return, Moses gives editing advice and abundant moral support. "I need constant cheerleading," admits Nina, a little shame-faced. "I'll write half a page and say, 'What do you think?' He's great at saying, 'It's good, keep going.'"

Her parents, she says, can be her fiercest critics. Her mum is given to pronouncing earnestly: "'I just don't think it's realistic.' She's very encouraging, but can be quite devastating. And my dad has a complete nose for when something is going on too long or being repetitive or sentimental." She's learned to roll with the punches: "I thought I was vulnerable, but you surprise yourself. You have to be quite robust or you wouldn't be able to exist."

• Tribes opens at the Royal Court, London SW1, on Thursday. Box office: 020-7565 5000.